Almost 30 people stabbed by a teenager at Berlin's new railway station are receiving protective treatment after it emerged one victim was HIV positive.
Crowds had gathered to watch a firework display at the station
The drunken youth carried out the stabbings at random as people left the opening ceremony at the station - Europe's largest - on Friday.
Only four of the injured remain in hospital, but authorities said 28 had been given a course of medication.
Police said a 16-year-old youth had been arrested over the attacks.
Berlin's Charite hospital head doctor Dirk Schuermann told Reuters news agency that HIV prophylatic treatment had been started for the victims after the incident at the city centre Hauptbahnhof.
"The chance of an HIV infection through a knife wound is three in 1,000. The prophylaxis can reduce the risk by another 80%," he said.
At least three more people have come forward since the attacks to say they have been stabbed, in response to a police appeal.
The 700m euro (£480m) station was inaugurated by German Chancellor Angela Merkel.
A two-day celebration was staged to mark the occasion, with the station formally opening on Sunday - just two weeks before Germany hosts the football World Cup.
But the festivities were marred when the teenager attacked some of the 500,000 spectators leaving the dedication ceremony, in what was reported to be a 10-minute rampage.
Fifteen of the victims had serious wounds when they were taken to hospital after the attack.
A youth was arrested in Berlin's government district over the attacks.
The glass-roofed railway station has been built close to where the Berlin Wall once cut through the capital.
The station took eight years to build and for the first time will link the railway lines in the north and south of Berlin with those in the east and west.